Question

Chrome iron ore (x) was heated with dry `Na_(2)CO_(3)` in the presence of quick lime and air in a furnace. The mixture was extracted with water and filtered. The filtrate was yellow(A) which on adding conc. `H_(2)SO_(4)` turned to orange red. The solution was evaporated and cooled. The crystals of B were obtained. To the crystals in aqueous solution, `NH_(4)Cl` was added. On fractional crystallization, orange red crystals (C ) is formed.
The oxidation states of chromium in x,A and C are
A. `+6,+6,+6`
B. `+3,+3,+3`
C. `+3,+6,+6`
D. `+3,+3,+6`

Answer 1

Correct Answer - C
`x:Fe(CrO_(2))_(2):+3,B:Na_(2)CrO_(4)`
and `(NH_(4))_(2)Cr_(2)O_(7):+6 and `+6`